By abdicating, the 75-year-old Beatrix is following a recent tradition. The BBC notes that "Queen Beatrix's mother Juliana resigned the throne in 1980 on her 71st birthday, and her grandmother Wilhelmina abdicated in 1948 at the age of 68."

The royal couple have three daughters: "Their first child, Princess Catharina-Amalia, was born on 7 December 2003. Their second child, Princess Alexia, was born on 26 June 2005, and their third child, Princess Ariane, on 10 April 2007."

After Beatrix signed the abdication papers, mother and son shared an emotional moment on the royal palace balcony in Amsterdam, tightly holding hands as she introduced him as king to the cheering crowd. He planted a kiss on his his mother's cheek.

Later, at the investiture ceremony before the Dutch parliament and royal visitors from around the world, the new king addressed her again.

"You did not go for popularity competitions," he said, according to a translation provided by the BBC. "You kept a stable and pure course because you know you are part of a long tradition. ... Your wisdom and your warmth will always be carried with me."

The former queen will now be known as Princess Beatrix.

Onlookers thronged Dam Square in Amsterdam to watch and hear the king nad queen on huge TV screens. Orange hats, shirts and flags dominated the scene.

"A big majority of the Dutch people still really believe in Holland as a monarchy," says Tim de Wit, a Berlin correspondent for Dutch NOS radio. "People really feel their 'orange' hearts beat and hope they will be ticking for a long time to come."

Still, not everyone in Holland is convinced that the monarchy should continue, especially in its ceremonial form today.

Critics question the tens of millions of dollars spent on the royal family each year, which its members pay no taxes on. King Willem-Alexander, for example, receives about $7 million in salary and expenses.

"Such sums are a bit overdone in a day in which the Netherlands has imposed drastic cuts on government subsidies for other forms of theater," wrote novelist Arnon Grunberg in a sarcastic essay that was published by The New York Times' op-ed section on Sunday. "Now that theaters, opera houses and museums cannot exist without sponsors, perhaps it's time for the Dutch to resign themselves to having a royal family that during state visits and official occasions, subtly drops the messages that this visit was brought to you in part by Royal Dutch Shell."

The new king is working to maintain good relations with his people. In a recent interview, he promised that his reign will be more informal.

"I'm not a protocol fetishist," he told a Dutch interviewer earlier this month, adding that it's up to his people whether they want to call him "your majesty" or not.